Digital lighting technologies such as light-emitting diodes (LEDs) offer significant advantages over incandescent and fluorescent lamps. These advantages include, but are not limited to, better lighting quality, longer operating life, and lower energy consumption. Consequently, LED-based lamps are increasingly being used to replace legacy light sources in conventional lighting fixtures. However, a number of design challenges and costs are associated with replacing traditional lamps with LED illumination devices. These design challenges include light production, thermal management, and manufacturing cost control.
By the very nature of their design and operation, LEDs have a directional light output. Consequently, employing LEDs to produce light distribution properties approximating or equaling the light dispersion properties of traditional lamps may require the costly and labor-intensive replacement or reconfiguration of the host light fixture, and/or the expensive and complexity-introducing design of LED-based solutions that minimize the installation impact to the host light fixture. Often material and manufacturing costs are lost in this trade off.
Another challenge inherent to operating LEDs is heat. When an LED operates in a high-temperature ambient environment and/or a space-limited enclosure, the heat generated by an LED and its attending circuitry can cause overheating and premature failure of the LED. Thermal management describes a system's ability to draw heat away from an LED. Passive cooling technology, such as a heat sink thermally coupled to a digital illumination device, may be used to transfer heat from a solid material to a fluid medium such as, for example, air. To prevent overheating of the LED, a heat sink must be designed to absorb and dissipate heat at a sufficient rate with respect to the amount of heat being generated by the LED. If the heat sink does not have the optimal amount of capacity, the heat can gradually build up behind the LED and cause damage to the components.
The heat dissipation requirements of common digital lighting solutions, as well as the limitations imposed by legacy light fixture designs, also can add cost and complexity to lighting assembly manufacturing. For example, external heat sinks typically are exposed to the visibility of consumers and, therefore, are often painted during manufacturing for aesthetic purposes. Painting heat sinks adds material and manufacturing costs to the overall price of the lamp product. Furthermore, the addition of circuitry to cause an LED-based luminaire to mimic the operational characteristics of a legacy lighting device also adds material and manufacturing costs. The lighting industry is experiencing advancements in design of LED-based lighting devices, some of which may be pertinent to certain aspects of manufacturing replacement lighting devices for legacy lamps.
U.S. patent application Ser. No. 12/910,340 by Sagal discloses at least one LED mounted on the exterior side of an electronic circuit board, and a thermally conductive housing material overmolded onto a peripheral portion of the electronic circuit board to form a heat sink. Such a molding method is designed to deliver product consistency and reliability. This molding method may, however, be difficult to maintain when manufacturing lamps with a multi-component design due to the typically labor-intensive and error-prone conventional hand assembly or semi-automated assembly processes employed.
U.S. patent application Ser. No. 13/149,179 by Chuang discloses an LED light bulb comprising a light source baseboard securely coupled to a heat sink. The fins of the heat sink are externally exposed to the environment surrounding the bulb and extend substantially near the base of the bulb. Similarly, U.S. patent application Ser. No. 12/987,104 by Huang discloses an LED light bulb with all of its heat sink fins fully exposed to contact with external air. As described above, the disclosed heat sink solutions both use fins that occupy most available circumferential space projecting outward from the surface of the heat sink, leaving no room for auxiliary devices. Also, because external heat sinks of such a design are predominately exposed to the visibility of consumers, the heat sinks are often painted during manufacturing for aesthetic purposes. Painting heat sinks adds material and manufacturing costs to the overall price of the lamp product.
U.S. patent application Ser. No. 12/649,631 by Ruffin discloses a heat sink for use with a high output LED light source. The heat sink comes into thermal contact with groups of outer vanes to increase the total heat dissipation surface area available to the light source. However, no thermal insulation exits between the fins of the heat sink and the LEDs to more effectively keep dissipated heat and ambient environment heat from reaching the LED light source. Lamp designs like those disclosed by Ruffin and the other designs described above typically feature heat sinks with fins extending toward the back of a lamp. Such designs suffer from unfavorable heat dissipation characteristics when used in a space-limited environment such as a can light fixture because much of the heat generated by LEDs comes out the back of the lamp itself.
Accordingly, and with the above in mind, a need exists for an LED-based luminaire design that supports simplified manufacturing of a luminaire that meets the operational and aesthetic requirements of consumers. More specifically, a need exists for a luminaire design that facilitates automated assembly and that minimizes costly and error-prone hand assembly and semi-automated assembly processes. A luminaire design is needed that employs thermal insulation to effectively keep dissipated heat and ambient environment heat from reaching an LED-based light source on the luminaire, particularly when the luminaire employed in a space-limited environment such as a can light fixture. A design is needed for a luminaire that provides passive cooling capability while reserving space on the structure of the luminaire for auxiliary devices. Furthermore, a luminaire design is needed for a luminaire that is aesthetically pleasing to a consumer but may be fabricated without adding the material and manufacturing costs of painting or otherwise covering passive cooling components.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.